The invention relates to power systems and methods and, more particularly, to power systems and methods employing generators.
Power systems for facilities may serve critical, life safety and other types of loads that require high availability. A typical power system for such a facility, therefore, may include an auxiliary generator, such as a diesel-powered motor-generator set, which may supply power to these loads when a primary power source, such as a utility source, fails.
A typical emergency backup power system may include a wound-field synchronous generator. Typically, in response to a loss of utility power, the load bus of the system is disconnected from the utility source and facility loads are disconnected from the load bus. The generator motor is started and accelerated and a field voltage applied to the rotor field windings to regulate the output voltage. The generator typically remains disconnected from the load bus until the synchronous generator achieves an output voltage and frequency control within acceptable limits. Loads may be selectively connected to the load bus after the generator energizes the load bus. Connection of a load may cause voltage and frequency fluctuations that can further delay connection of additional loads.
Thus, the time required to bring such a generator fully on line may include time required to detect the outage, time required to decouple the load bus from the utility source, time to disconnect the loads from the load bus, time to bring the generator tip to an acceptable voltage and frequency, time to connect the generator to the load bus and time to connect loads to the load bus. These operations may take on the order of several seconds, which may negatively affect the availability of certain loads.